Environment-friendly dual-mode immunoassay based on the inner filter effect of polydopamine-polyethylenimine copolymer nanoparticles for the highly sensitive detection of norfloxacin

In this study, we synthesized a polydopamine-polyethyleneimine (PDA-PEI) copolymer nanoparticles (NPs) fluorophore by a simply and environment-friendly one-step self-assembly reaction at room temperature to minimize environmental pollution and resource waste caused by the extensive use of organic solvents for material synthesis and sample pretreatment in immunoassay. Based on the inner filter effect between the synthesized PDA-PEI NPs fluorophore and p-nitrophenyl that produced by alkaline phosphatase catalyzed p-nitrophenylphosphate, we proposed one novel and environment-friendly fluorometric/colorimetric dual-mode enzyme-linked immunosorbent assay for the highly sensitive detection of norfloxacin (NOR) in various samples without organic solvents and highly irritating acid-base solutions. After comprehensive optimization, the detection limits of the two modes of immunoassays were 0.02–0.75 μg/kg with recovery rates of 75.38 % ∼ 109.50 % in four types of meat and two waters. Finally, the established simple, highly sensitive, and robust immunoassay offers a powerful tool for NOR detection in various food and environmental samples.